# math

A man who can swim at 5km/h in still water swims towards the east to cross arriver. If the river flows from north to south at the rate of 3km/h
a) Calculate:
i) The resultant speed
ii) The drift
b) If the width of the river is 30m, find the time taken, in seconds, for the man to cross the river

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1. X = 5 km/h
Y = -3 km/h

i. Speed = Sqrt(X^2+Y^2) = sqrt(5^2+3^2)= 5.83 km/h = 1.62 m/s.

b. Tan A = Y/X = -3/5 = -0.60
A = -31o = 31o S. of E.

d = 30m/Cos(-31) = 35 m. = Distance to cross.

d = V*t = 35 m.
t = 35/V = 35/1.62 = 21.6 s.

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